Centrifugal casting apparatus for dental purposes



In venton:

C. FRITZSCHE July so, 1935.

CENTRIFUGAL CASTING APPARATUS FOR DENTAL PURPOSES Filed Oct. 18, 1933 Patented July 30,1935

UNITE CENTRIFUGAL CASTING APPARATUS FOR DENTAL PURPOSES Curt Fritzsche, Leipzig, Germany 1 Claim.

It is well known to produce castings, in particular for dental work, by centrifugal casting processes. In such cases it is usual to make the mould of ceramic material according to a pat- 5 tern or model which has previously been prepared in wax. This procedure has a number of disadvantages.

The chief disadvantage is that the density of the casting, in so far as it is made of metal, is impaired because the metal absorbs or occludes gases during the usual melting process and these gases are again in part released when the metal cools and thereby make the casting porous. The use of a protective atmosphere, for example of nitrogen, is no protection against this.

Now the invention relates to a method of producing thin-walled castings, in particular for dental purposes, which are true to pattern, whereby this disadvantage is obviated.

In the method according to the invention, the melting and casting of the metal and its cooling is undertaken in a centrifugal casting apparatus which is contained in a vacuum chamber. Either the centrifugal apparatus including the driving motor may be arranged in the vacuum chamber, or the driving means for the centrifugal apparatus may be arranged outside the chamber and the drive taken through a stuffing box provided in a wall of the vacuum chamber.

Two' forms of apparatus for carrying out the new method are illustrated by way of example in the accompanying drawing, in which:

Fig. 1 is an elevation partly in vertical section of a form in which the centrifugal apparatus is arranged entirely within the vacuum chamber, and

Fig. 2 illustrates in plan a form in which the centrifugal apparatus is arranged in the vacuum chamber and is driven from a source of power arranged outside the vaccum chamber.

Referring to the drawing, in the vacuum chamber I is fitted a frame 2 which carries the vertical shaft 3 of the centrifugal apparatus. The numeral 4 designates an electric motor the rotation of which is transmitted to the shaft 3 by way of the bands and pulleys 5. On a, horizontal arm 6 which is fast on the shaft 3 is mounted at one end the casting furnace 8 and at the other end a counterweight 1. Electric current is supplied to the furnace 8 through the slip rings 9. The numeral l designates the crucible and the numeral II the hollow mould while l2 represents a tube for making the connection to the vacuum chamber.

Referring now to Figure 2, in this figure like parts are designated by like reference numerals. The electric motor 4 is located outside the vacuum chamber I. By means of the arrangement I3 the drive is taken air-tightly through one wall of the vacuum chamber 1 so that the rotation of the parts is transmitted to a shaft I 4 which 10 again transmits its rotation by means of the driving mechanism IE to the centrifugal shaft 3.

In carrying out the casting, the metal or other mass, for example a metal alloy or a ceramic mass, which has to be melted and cast is melted in the electrically heated furnace 8 which contains the mould H and is arranged in the vacuum vessel I. Before the melting of the metal begins a vacuum must be produced in the chamber I. When the metal has melted the shaft 3 is rotated so that the molten metal flows into the mould under high centrifugal pressure, while the vacuum within the vessel I is still maintained. After disconnecting the heating current the casting is allowed to remain in the vacuum until it solidifies.

The advantages of this process are that the metal or other cast mass can absorb no gases and therefore none can again be given off on solidification. Preferably," in so far as metals are used for the casting, metals or metal alloys melted in the vacuum are employed.

I claim:

In a manufacturing process for manufacturing thin walled castings and in combination an apparatus comprising a vacuum chamber, an inlet communicating with a vacuum source, a rotatably arranged shaft inside of said chamber and extended with an airtight fit through the wall of the chamber to the outside, driving means connected with said shaft end, a horizontal bar fixed crosswise to the shaft, an electrically heated furnace attached to one end of said bar, a crucible and a hollow mould communicating therewith inside of a said furnace, slip rings adapted to transmit the current to the furnace and a counterweight attached to the other end of the cross bar.

CURT FRITZSCHE. 

